1. Field of the Invention
The present invention relates to a gas turbine seal system between a stationary blade shroud and an adjacent moving blade platform.
2. Description of the Related Art
FIG. 4 is a cross sectional view which shows an arrangement of a stationary blade and a moving blade in a conventional gas turbine. In the drawing, reference numeral 21 denotes a moving blade, and reference numeral 31 denotes a stationary blade. The moving blade 21 has a platform 22 in a base portion, and is alternately mounted to a rotor with the stationary blade 31 being disposed therebetween. Also, car the moving blades are rotated by a flow of a combustion gas 50. Reference numeral 23 denotes a seal plate provided at the front and rear of a lower portion of the 19 platform 22, and reference numerals 24 and 25 denote a front end portion and a rear end portion, respectively, of the platform 22.
Reference numeral 32 denotes an inside shroud of the stationary blade 31, and reference numerals 33 and 34 denote a front end portion and a rear end portion thereof, respectively. Reference numeral 35 denotes a cavity disposed below the shroud 32, reference numeral 36 denotes a seal box, and reference numerals 37 and 38 denote spaces formed between the adjacent moving blades 21 in a front and rear direction, and these spaces are under high pressure due to sealing air flowing out from the cavity 35 and the seal box 36, etc.
In the gas turbine having the structure described above, the high temperature combustion gas 50 flows through a combustion gas passage formed by the moving blade 21 and the stationary blade 31 and causes the moving blade 21 to rotate in order to drive the gas turbine. During operation of the turbine, sealing air flows into the cavity 35 from the inner portion of the stationary blade 21 through a passage (not shown), thereby increasing the pressue in cavity 35 to a high pressure, so that the high temperature combustion gas 50 is prevented from entering the blade from the combustion gas passage.
At this time, the sealing air flows out in an upward direction from between the end portion 33 of the inside shroud 32 of the stationary blade 31 and the end portion 25 of the platform 22 of the moving blade 21, and between the end portion 34 of the inside shroud 32 and the end portion 24 of the platform 22, respectively. As shown by an arrow 40, the sealing air flows in a substantially perpendicular direction relative to the combustion gas 50 which flows in an axial direction, thereby increasing flow resistance of the combustion gas 50.
As mentioned above, in the conventional gas turbine, the sealing air 40 flows out from between the shroud of the stationary blade and the platform of the adjacent moving blade in a direction substantially perpendicular to the flow of the combustion gas 50 thereby increasing the flow resistance of the combustion gas 50, and resulting in deteriorated performance of the turbine.